Field specifiers

You use field specifiers to say what value from the topic you are interested
in.

All meta-data in a topic is referenced according to a simple plan.

name - name of the topic

web - name of the web the topic is within

text - the body text of the topic (without embedded meta-data)

META:FILEATTACHMENT

for each attachment

name

attr

path

size

user

rev

date

comment

META:TOPICPARENT

name

META:TOPICINFO

author

date

format

version - topic version (integer)

META:TOPICMOVED

by

date

from

to

META:FORM - the main form of the topic

name

META:FIELD - the fields in the form.

for each field in the form

name - name of the field

title - title of the field

value - what is stored in the field

form - name of the form the field is in (currently always equal to META:FORM.name)

attributes - string stored in the attributes, like H for hidden

META:PREFERENCE

for each preference in the topic

name

value

See MetaData for details of what all these entries mean. Note that the set
of meta-data types (and the aliases used to refer to them) may be extended
by Foswiki extensions.

Most things at the top level of the plan - META:TOPICPARENT, META:TOPICINFO etc - are structures which are indexed by keys. For example, META:TOPICINFO has 4 entries, which are indexed by the keys author, date, format and version. META:FILEATTACHMENT, META:FIELD and META:PREFERENCE are all arrays, which means they can have any number of records under them. Arrays are indexed by numbers - for example, the first entry in the META:FIELD array is entry 0.

It's a bit clumsy having to type META:FILEATTACHMENT every time you want to refer to the array of attachments in a topic, so there are some predefined aliases that make it a bit less typing:

attachments means the same as META:FILEATTACHMENT

info means the same as META:TOPICINFO

parent means the same as META:TOPICPARENT. Note:parent is itself a map; use parent.name to access the name of the parent topic

moved means the same as META:TOPICMOVED

form means the same as META:FORM, so to test if a topic has a form named 'UserForm' you test for "form.name ~ '*.UserForm'"

fields means the same as META:FIELD, You can also use the name of the form (the value of form.name e.g. PersonForm)

preferences means the same as META:PREFERENCE

extensions may add additional aliases when they register new meta-data types

Fields in this plan are referenced using a simple field specifier syntax:

where X is an array and N is an integer number >= 0, gets the Nth element of the array X. If N is a floating point number, the integer part will be used as the index. Negative indices can be used to index the array from the end e.g. attachments[-1] to get the last attachment.

attachments[3]

X/Y

accesses Y from the topic specified by the value of X. X must evaluate to a topic name

parent.name/(form.name='ExampleForm') will evaluate to true if (1) the topic has a parent, (2) the parent topic has the main form type ExampleForm.

{X}

expands to the value of the configure setting {X}, if it is accessible, or '' otherwise

Note: at some point Foswiki may support multiple forms in the same topic. For this reason you are recommended not to use the fields shortcut when accessing form fields, but always use the name of the form instead.

If you use the name of a field (for example, LastName) in the query without a . before it, that is taken to mean "the value of the field named this". This works if and only if the field name isn't the same as of the top level entry names or their aliases described above. For example, the following expressions will all evaluate to the same thing:

PersonForm[name='Lastname'].value

Lastname

PersonForm.Lastname

If X would conflict with the name of an entry or alias (e.g. it's moved or maybe parent), you can prepend the name of the form followed by a dot, as shown in the last example.

Constants

You use constants for the values that you compare with fields. Constants are either strings, or numbers.

String Constants

String constants are always delimited by single-quotes. You can use backslash \ to include the following special characters:

LHS is less than RHS. If both sides are numbers, the order is numeric. Otherwise it is lexical (applies to all comparison operators)

>

greater than

<=

less than or equal to

>=

greater than or equal to

lc(x)

Converts x to lower case, Use for caseless comparisons.

uc(x)

Converts x to UPPER CASE. Use for caseless comparisons.

d2n(x)

Converts a text string representing a date (expressed in one of the formats that Foswiki can parse) to a number of seconds since 1st Jan 1970. This is the format dates are stored in inside Foswiki, and you have to convert a string date using d2n before you can compare it with - for example - the date an attachment was uploaded. Times without a timezone are assumed to be in server local time. If the text string is not recognised as a valid date, then d2n will return undefined.

You can get the current time for date comparisons using SpreadSheetPlugin, thus: %CALC{"$TIME()"}%

If you want to know if a field is undefined (has never been given a value) then you can compare it with undefined (this requires that no field called undefined exists in the form).

In the operators ( = != ~ =~ < > <= >= NOT AND OR) an undefined operand is treated the same as numerical 0. For lc uc d2n an undefined operand will give an undefined result. For length and undefined operand will give a result of 0.

Putting it all together

When a query is applied to a topic, the goal is to reduce to a TRUE or FALSE value that indicates whether the topic matches that query or not. If the query returns TRUE, then the topic is included in the search results.

A query matches if the query returns one or more values when it is applied to the topic. So if I have a very simple query, such as "attachments", then this will return TRUE for all topics that have one or more attachments. If I write "attachments[size>1024 AND name ~ '*.gif']" then it will return TRUE for all topics that have at least one attachment larger than 1024 bytes with a name ending in .gif.

Gotcha

Remember that in the query language, topic names are constants. You cannot write Main.UserTopic/UserForm.firstName because Main.UserTopic will be interpreted as a form field name. If you want to refer to topics you must enclose the topic name in quotes i.e. 'Main.UserTopic'/UserForm.firstName

Examples

Query examples

attachments[name='purdey.gif'] - true if there is an attachment call purdey.gif on the topic

(fields[name='Firstname'].value='Emma' OR fields[name='Firstname'].value='John') AND fields[name='Lastname'].value='Peel' - true for 'Emma Peel' and 'John Peel' but not 'Robert Peel' or 'Emma Thompson'

(Firstname='Emma' OR Firstname='John') AND Lastname='Peel' - shortcut form of the previous query

HistoryForm[name='Age'].value>2 - true if the topic has a HistoryForm, and the form has a field called Age with a value > 2

HistoryForm.Age > 2 - shortcut for the previous query

preferences[name='FaveColour' AND value='Tangerine'] - true if the topic has the given preference settings and value

Person/(ClothesForm[name='Headgear'].value ~ '*Bowler*' AND attachments[name~'*hat.gif' AND date < d2n('2007-01-01')]) - true if the form attached to the topic has a field called Person that has a value that is the name of a topic, and that topic contains the form ClothesForm, with a field called Headgear, and the value of that field contains the string 'Bowler', and the topic also has at least one attachment that has a name matching *hat.gif and a date before 1st Jan 2007. (Phew!)

length(fields[NOT lc(attributes)=~'h']) - the number of fields that are not hidden

Search examples

Find all topics that are children of this topic in the current web

%SEARCH{"parent.name = '%TOPIC%'" web="%WEB%" type="query"}%

Find all topics that have an attachment called 'grunge.gif'

%SEARCH{"attachments[name='grunge.gif']" type="query"}%

Find all topics that have form ColourForm where the form field 'Shades' is 'green' or 'yellow' but not 'brown'